Amorphous metal alloy materials have become of interest in recent years due to their unique combinations of mechanical, chemical and electrical properties that are especially well-suited for newly-emerging applications. Examples of amorphous metal material properties include the following:
uniform electronic structure,
compositionally variable properties,
high hardness and strength,
flexibility,
soft magnetic and ferroelectronic properties,
very high resistance to corrosion and wear,
unusual alloy compositions, and
high resistance to radiation damage.
These characteristics are desirable for applications such as low temperature welding alloys, magnetic bubble memories, high field superconducting devices and soft magnetic materials for power transformer cores.
The unique combination of properties of amorphous metal alloy materials may be attributed to the disordered atomic structure of amorphous materials which ensures that the material is chemically homogeneous and free from the extended defects that are known to limit the performance of crystalline materials.
Generally, amorphous materials are formed by rapidly cooling the material from a molten state. Such cooling occurs at rates on the order of 10.sup.6 .degree. C./second. Processes that provide such cooling rates include sputtering, vacuum evaporation, plasma spraying and direct quenching from the liquid state. Direct quenching from the liquid state has found the greatest commercial success since a variety of alloys are known that can be manufactured by this technique in various forms such as thin films, ribbons and wires. U.S. Pat. No. 3,856,513 to Chen et al. describes novel metal alloy compositions obtained by direct quenching from the melt and includes a general discussion of this process. Chen et al. describes magnetic amorphous metal alloys formed by subjecting the alloy composition to rapid cooling from a temperature above its melting temperature. A stream of the molten metal is directed into the nip of rotating double rolls maintained at room temperature. The quenched metal, obtained in the form of a ribbon, was substantially amorphous as indicated by x-ray diffraction measurements, was ductile, and had a tensile strength of about 350,000 psi.
U.S. Pat. No. 4,036,638 to Ray et al. describes binary amorphous alloys of iron or cobalt and boron. The claimed amorphous alloys were formed by a vacuum melt-casting process wherein molten alloy was ejected through an orifice and against a rotating cylinder in a partial vacuum of about 100 millitorr. Such amorphous alloys were obtained as continuous ribbons and all exhibited high mechanical hardness and ductility.
The thicknesses of essentially all amorphous foils and ribbons formed by rapid cooling from the melt are limited by the rate of heat transfer through the material. Generally the thicknesses of such films are less than 50 .mu.m. The few materials that can be prepared in this manner include those disclosed by Chen et al. and Ray et al.
Amorphous metal alloy materials prepared by electrodeposition processes have been reported by Lashmore and Weinroth in Plating and Surface Finishing, 72 (August 1982). These materials include Co-P, Ni-P, Co-Re and Co-W compositions. However, the as-formed alloys are inhomogeneous and so can be used in only limited applications.
The above-listed prior art processes for producing amorphous metal alloys depend upon controlling the kinetics of the solidification process; controlling the formation of the alloy from the liquid (molten) state or from the vapor state by rapidly removing heat energy during solidification. The known amorphous metal alloys and processes for making such alloys discussed above suffer from the disadvantage that the so-formed amorphous alloy is produced in a limited form, that is, as a thin film such as a ribbon, wire or platelet. These limited shapes place severe restrictions on the applications for which amorphous metal materials may be used.
To produce bulk amorphous metal alloy objects the formed amorphous alloy must be mechanically and physically reduced to a powder as by chipping, crushing, grinding and ball milling, and then recombined in the desired shape. These are difficult processes when it is realized that most amorphous metal alloys have high mechanical strengths and also possess high hardnesses.
In Applicants' co-pending U.S. patent application, Ser. No. 586,380, filed Mar. 5, 1984, entitled "Amorphous Metal Alloy Powders and Synthesis of Same By Solid State Decomposition Reactions", there is disclosed a novel process by which amorphous metal alloys may be synthesized as powders. This process is a solid state reaction that produces an intimate mixture of the components of the amorphous metal alloy powders from precursor compounds. The above disclosure is incorporated herein by reference.
We have now discovered an improvement for the formation of amorphous bulk objects. It is therefore, one object of this invention to provide novel bulk amorphous metal alloy objects.
It is another object of the present invention to provide a process for the synthesis of bulk amorphous metal alloy objects.
These and additional objects of the present invention will become apparent in the description of the invention and examples that follow.